A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
The tile can be had by selecting the rectangle in Inkscape and using shift+alt+i. Remixed from a drawing in 'Flowers of Song', Frederick Weatherly, 1895.
Source Firkin
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
Zero CC tileable dry grass texture, photographed and made by me. CC0
Source Sojan Janso
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A seamless pattern formed from a tile made from page ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau
Remixed from an image that was uploaded to Pixabay by KirstenStar
Source Firkin
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A new take on the black linen pattern. Softer this time.
Source Atle Mo
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A yellow tiled background... Blurriness, bokeh effect and rectangles pattern in one mix.
Source V. Hartikainen
Green Background Pattern
Source V. Hartikainen
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
Inspired by a pattern I saw in a 19th century book. This seamless pattern was created from a square tile. To get the tile, select the pattern in Inkscape and use shift+alt+i.
Source Firkin